<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let o =prompt('计算符号')
        let i = + prompt('数字1')
        let j = + prompt('数字2')
       switch (o){
        case '+':
           alert(i+j)
           break
        case '-':
            alert(i-j)
            break
         case '*':
            alert(i*j)
            break
        case '/':
        alert(i/j)
        break
       }
        
    </script>
</body>
</html>